Method of manufacturing twisted tubes

Abstract

A method of manufacturing a spiral tube including the steps of positioning an elongated mandrel within a tube, grasping the ends of the tube, forming a point of reduced resistance to torsional force in the wall of the tube, rotating one end of the tube while the other end is held stationary to cause the formation of a spiral groove in the tube, the mandrel defining the minimum interior diameter of the spiral tube so formed, and advancing the means grasping the tube towards each other to compensate for the reduction of length of the tube as the spiral groove therein is formed, and maintaining at least the area of the tube at which the spiral groove is being formed at an elevated temperature.

What is claimed is: 
     
       1. A method of manufacturing a spiraled tube comprising: (a) positioning an elongated cylindrical mandrel within a tube;   (b) grasping the tube adjacent the first end with a motor driven headstock;   (c) grasping the tube adjacent the second end with a non rotating tailstock;   (d) forming at least one point of reduced resistance to torsional force on the wall of the tube, which step may be accomplished before or after steps (a) and (b);   (e) rotating the headstock by means of said headstock motor to initiate and extend the formation of at least one spiral groove in the tube, the mandrel defining the minimum interior diameter of the spiraled tube so formed;   (f) driving a first and a second lead screw by means of said headstock drive motor;   (g) advancing said tailstock towards said head stock by coupling said first lead screw to said tail stock to compensate for the reduction in length of the tube as the spiral groove is formed;   (h) supporting a heating element adjacent the tube;   (i) advancing said heating element towards said headstock by means of said second lead screw whereby said heating element is positioned adjacent the area of the tube wherein spiral groove is formed as the tube is rotated to raise the area of formation of the spiral groove to a temperature above ambient and below the melting point of the tube material.   
     
     
       2. A method of manufacturing a spiraled tube according to claim 1 wherein said heating means is in the form of electroinductive means. 
     
     
       3. A method of manufacturing a spiraled tube according to claim 1 wherein said heating means is in the form of gas flame means.